Building the Wiring Harness
It turned out that the TJ swap diagrams didn’t match anything I had. It appeared that my transmission was an earlier model with different connectors and of course the wiring for the YJ was completely different from that of the TJ. However, being an old electronics man, I was completely undaunted. I went to AllData and downloaded the appropriate wiring diagrams for the 1993 Wrangler and the 1997 Cherokee, and cross referencing them, I developed my own interconnection diagram. As it turned out, all of the signals needed for the XJ transmission and TCU were available right at the YJ PCU connector. So it was simply a matter of splicing the transmission and TCU wires into the appropriate wires of the YJ PCU harness. There was only one signal that had to go to a place other than the PCU and that was the 12 volts to illuminate the backup lights. I tied that into an existing YJ connector just to the right of the transmission.
The first task was to extract the transmission and TCU portions from the XJ wire harness. Others have just cut the connectors off the harness leaving short pig tails. I wanted to keep as much of the harness together as possible. Using the appropriate connecter pin-out diagrams I identified each wire. The wires that ran between the two transmission connecters and the TCU connector I left intact. Any wires that went from these connectors to other parts of the XJ harness, I cut and labeled, as they would be spliced into the YJ PCU harness.
This is the end result. The two connectors on the upper right attach to the transmission harness, a 6-way and an 8-way. The other 21 pin rectangular connecter at the top plugs into the TCU. The wires that are unattached at one end are to be spliced into the vehicle harness. At this time I left the firewall grommet on the harness as I wasn't sure whether or not I would use it. As it turned out, I later removed it and routed the harness through the firewall through an existing grommet.
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